The purpose of this study is to suggest how to use the phase diagram for water to explain the evaporation and sublimation in lhe atmospheric condition. In principle, the phase diagram for water represents a one component system so it cannot be applied to the water contact with lhe air. When the liquid or solid phase of water exists in the air, always water vapor also exists in the air. In this case, we cannot present this state as a single point on the phase diagram because the pressure of the liquid or solid is different from that of the vapor in the air. However, since the saturation vapor pressure of liquid or solid is altered by negligible amount due to tbe presente of air, the evaporation and sublimation in the atmospheric condition can be explained using the vapor pressure line and sublimation line on the phase diagram.